This application claims the priority of Korean patent application Serial No. 2000-46691 filed on Aug. 11, 2000.
This application claims the benefit of Korean Patent Application No. 2000-46691, filed on Aug. 11, 2000, under 35 U.S.C. xc2xa7 119, the entirety of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a method of forming a titanium nitride (TiN) thin film, and more particularly, to a MOCVD (Metal Organic Chemical Vapor Deposition) method using TDEAT (Tetrakis Diethylamino Titanium) as a precursor.
2. Description of Related Art
A titanium nitride (TiN) film is usually formed by a sputtering method due to the fact that this method results in excellent film characteristics and has simplicity in the process. However, as microelectronics devices have become integrated, the TiN thin film requires superior step coverage. Therefore, a CVD (Chemical Vapor Deposition) method that uses TiCl4 and NH3 as reaction gas is developed. Although the TiN thin film formed by CVD (referred to as CVD-TiN) which employs TiCl4 has the superior step coverage, a process temperature of this CVD should be equal to or more than 600 degrees Celsius (xc2x0 C.) in order to make TiN thin film include a low chlorine (Cl) content. Therefore, this CVD method employing TiCl4 is not adequate to a TiN thin film of a multi-layer line formation process or a Dow temperature process.
Accordingly, a metal organic CVD-TiN (MOCVD-TiN) deposition process which can process TiN thin film at a low temperature is researched and developed. A precursor for use in the MOCVD-TiN deposition process is usually Tetrakis DiMethylAmido Titanium (TDMAT, Ti[N(CH3)2]4), Tetrakis DiEthylAmido Titanium (TDEAT, Ti[N(C2H5)2]4) or Tertakis EthylMethylAmido Titanium (TEMAT, Ti[N(C2H5)2]4). However, the TiN thin film contains a lot of carbon when depositing these precursors via thermal decomposition. In order to overcome this problem, various methods are researched and developed.
For example, in a case that TDMAT is used as the precursor, N2 or H2 plasma processing is conducted after TiN thin film is deposited. Namely, when the precursor is TDMAT, ammonia (NH3) gas easily reacts with TDMAT vapor and a carbon content in the TiN thin film decreases, thereby lowering firmness and stability of the TiN thin film. Therefore, the additional N2 or H2 plasma processing is required to improve the quality of the TiN thin film. However, some problems occur in this process. Since the plasma processing is necessary for the TiN thin film, a lot of particles are produced in a reaction chamber, and additionally, a process time is prolonged. Furthermore, the plasma processing is nonproperty conducted inside a contact hole. Thus, the TiN thin film quality in the contact hole is not so good when forming the TiN thin film into the contact hole. These demerits occurring in the contact hole will be more conspicuous as the contact hole diminishes in size.
In a case that TDEAT is used as a precursor, a TiN thin film has better quality than that in a case that TDMAT is used as the precursor. However, there are some limitations in use of TDEAT as a precursor. U.S. Pat. No. 5,139,825 discloses that the TiN thin film is formed in a wary of using transition metal amido compound as a precursor and using ammonia (NH3) gas. However, a process temperature is limited in the range of 100 to 400 degrees Celsius (xc2x0 C.). Furthermore, the process is operated at a pressure less than atmospheric pressure.
Additionally, U.S. Pat. No. 5,672,385 discloses that the thin film is formed using ammonia (NH3) gas and using TDEAT as a precursor. However, the pressure in the reactor is controlled at a value in the range of about 0.00075 to 0.1125 Torr. Further, according to the data shown in U.S. Pat. No. 5,672,385, although the step coverage is more or less improved, the resistively of the thin film is not improved.
FIG. 1 is a schematic diagram illustrating a conventional TiN thin film deposition apparatus that adopts a shower bead. As shown in FIG. 1, the conventional apparatus supplies vapor of a TDEAT precursor and ammonia (NH3) gas through the shower head 20 in order to form a TiN thin film. In other words, the TDEAT vapor and the ammonia (NH3) gas flow into a reaction chamber 10 through the shower head 20 that is disposed in a corresponding position over a susceptor 30. Then these vapor and gas are exhausted through an exhaust pipe 50 that is arranged at a bottom portion of the reaction chamber 10. A substrate 40 is put on the susceptor 30 and the TiN thin film is formed by reaction between the TDEAT vapor and the ammonia (H3) gas. Additionally, a heater (not shown) is installed in the susceptor 30 to form the TiN thin film on the substrate 40.
In the conventional TiN thin film deposition apparatus, however, there are some problems when using the shower head 20 as a gas injection device. For example, since the gas ejected from the shower head 20 directly moves towards and reaches the substrate 40, a lot of particles are generated in accordance with a sudden change of temperature. Furthermore, since the shower head 20 is close to and faces to the substrate 40 having the heater (not shown), the shower head 20 has a high temperature and it is very difficult to control a temperature of the shower head 20 independently.
Accordingly, the present invention is directed to a MOCVD (Metal Organic Chemical Vapor Deposition) method that substantially overcomes one or more of the problems due to limitations and disadvantages of the related art.
To overcome the problems described above, the present invention provides a MOCVD method using TDEAT as a precursor to form a titanium nitride (TiN) thin film on a substrate.
An object of the present invention is to provide a MOCVD method that forms a TiN thin film at a low temperature and that makes the TiN thin film include a low carbon content.
Another object of the present invention is to provide a MOCVD method that forms a TiN thin film having low resistivity and superior step coverage.
Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
In order to achieve the above object, a method of forming a titanium nitride (TiN) thin film on a substrate disposed on a susceptor in a reaction chamber, includes feeding vapor of a Tetrakis Diethylamino Titanium (TDEAT) precursor and ammonia (NH3) gas into the reaction chamber, wherein a ratio of a vaporization rate of the TDEAT precursor to a flow rate of the ammonia gas is a value in the range of 1 mg/min:20 sccm to 1 mg/min:100 sccm; maintaining an atmosphere in the reaction chamber at a pressure in the range of 0.5 to 3.0 Torr; and heating the substrate to a temperature in the range of 300 to 400 degrees Celsius (xc2x0 C.).
In this method, the substrate is heated up to a temperature in the range of 320 to 380 degrees Celsius (xc2x0 C.). The atmosphere in the reaction chamber bias a pressure in the range of 0.5 to 1.5 Torr.
The method of forming a titanium nitride (TiN) thin film further includes supplying a carrier gas, such as argon (Ar) and helium (He), into the reaction chamber at a flow rate in the range of 100 to 1000 sccm.
The method of forming a titanium nitride (TiN) thin film further includes vaporizing the TDEAT precursor before the TDEAT precursor is fed into the reaction chambers At this time, the TDEAT precursor is vaporized at a vaporization rate in a range of 10 to 50 mg/min. Additionally, the ammonia gas is fed to the reaction chamber at a flow rate in the range of 500 to 3000 sccm.
When using the above-mentioned method, the reaction chamber is a dome-shaped top portion and includes a plurality of gas injectors that supply the TDEAT vapor and the ammonia gas to the reaction chamber in an upward direction from the bottom to top portion of the reaction chamber. Additionally, the TDEAT vapor and the ammonia gas are respectively supplied by the different gas injectors.
The reaction chamber includes a heat exchanger on an outer surface thereof in order to maintain a top portion of the reaction chamber at a temperature in the range of 50 to 150 degrees Celsius (xc2x0 C.). Advisably, the heat exchanger maintains a top portion of the reaction chamber at a temperature in the range of 80 to 100 degrees Celsius (xc2x0 C.),
Furthermore, the heat exchanger can maintain a wall of the reaction chamber at a temperature in the range of 50 to 150 degrees Celsius (xc2x0 C.). Advisably, the heat exchanger maintains a wall of the reaction chamber at a temperature in the range of 80 to 100 degrees Celsius (xc2x0 C.),
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate one embodiment of the invention and together with the description serve to explain the principles of the invention.